This can be due to a corrupted .pck file or a conflict with the game's DRM.

If you hear ambient world sounds and music but no voices during cinematics, your PC's audio configuration might be set to 5.1 or 7.1 surround sound while you are using stereo speakers or headphones. Right-click the in your Windows taskbar. Select Sound Settings > More sound settings . Click your playback device and hit Configure . Set the audio channel to Stereo and test the game again.

Assassin’s Creed Brotherhood stores its audio data in the main installation directory. To restore English voices, you specifically need the following files:

When downloading and installing sound packs, it is essential to take precautions: